The term 'doughnut shape' is used to describe two different shapes: a torus (5 letters) and a TOROID (6 letters). A torus is a surface of revolution generated by revolving a circle in three-dimensional space about an axis coplanar with the circle. It is shaped like a doughnut, with a hollow center. A TOROID is a surface of revolution generated by revolving a closed curve, such as a circle, around an axis that does not intersect the curve. It is also shaped like a doughnut, but with a solid center. Both shapes are commonly referred to as doughnut shapes.